Re: Digitizers, Renishaw

> Roman Black wrote:
> > I would stay well away from electrical contacts.


> Well, there's the rub. The Renishaw design causes an open
> circuit when the contact probe is moved .0002" in ANY
> direction. I can see how this will work with an electrical contact
> between two hard, rigid parts. I can also see how bad contact
> could occur, as you say.
>
> I don't see an easy way to make a low-force probe that will detect
> such tiny motion in any direction by optical means.

Ok, are you saying the Renishaw device uses simple
make/break electrical contacts??

Second, .0002" is big by opto standards.
The simple laser unit in any cheap CD player
focuses MANY TIMES smaller than that, and
has a tiny chip attached to it that gives
amplification and a dc voltage output which
even has a little trimpot to adjust. I have
to fix these mongrels sometimes! ;o)

One of these would detect your 0.0002 easily,
even after the reduction from leverage
from pointer length to mount width.

But once you start getting the "mines smaller
than yours" thing happening isn't it going
to false trigger and stuff due to machine
vibration??
-Roman